This invention relates to a multiple tank filtration system which permits a high flow backwash. More particularly this invention relates to a filtration system which uses a tank connecting distributor which permits a high flow backwash of the media in the tanks. In addition, this invention relates to a method of regulating the filtration media in multiple tank filtration systems using a high flow backwash.
Most filtration systems consist of a single tank which contains the filtration media. In the instances where more than one type of media is to be used, the media will be layered in the tank. This layering can be with or without a separator membrane. The function of a separator membrane is to maintain the two different media separate and distinct. However, even when a separator membrane is used, there is a problem of maintaining the structural integrity of the filtration medium as during backwash. This is the case since the tanks are usually in a vertical orientation with the input water to be purified flowing downwardly. This serves to compact the media bed. However on backwash, the flow will be upwardly and the media bed will be disturbed. In a high flow backwash a multiple media bed will be disturbed to the extent that the media will become intermixed and generally the more dense media will end up at the bottom of the tank. This is the case even when a separator membrane is used. In some instances the membrane separator can become dislodged and the different media will flow around the membrane separator and become intermixed and at times the separator diverts flow which promotes channeling along the separator and tank walls with the result that the liquid does not effectively contact the media. This will result in a decreased efficiency for the unit.
This problem has been resolved by using a multiple tank system with a novel interconnector distributor. Multiple tank systems are also not known to have high flow characteristics. This is the case since the backwash liquid must be necked down at the tank juncture to flow the liquid from tank to tank. This will be a flow constricting point in the system. However by using the interconnector distributor of the present system, the backwash can be maintained at a high flow rate for a multiple tank system.
An advantage of this system is that a media such as an oxidation-reduction media can be used as the media in the first tank which is the tank into which the liquid flows and an adsorbent media used in the second tank. In this way, the media in the first tank will remove solid microparticles from the input liquid and permit better adsorption in the second tank. Also on backwash the backwash liquid will first contact the relatively cleaner adsorption media at a high flow rate and then the oxidation-reduction media which would contain metallic and other sediments also at a high flow rate. In this way these sediments will not contact and contaminate the adsorption media, but can still be removed from the other media since there will still be a high flow of liquid during backwashing the first tank. If the system contains three tanks the third tank can contain a water softener resin to remove calcium and magnesium ions. It is also an option that the second tank can contain the water softener resin while the third tank contains the adsorption media.